1. Field of the Invention
The present invention relates to recording thin film magnetic heads having a toroidal coil layer and used for floating type magnetic heads or the like, and more particularly, relates to a thin film magnetic head and a manufacturing method thereof, the thin film magnetic head having a large heat capacitance at a height direction side of a toroidal coil layer and superior heat dissipation properties.
2. Description of the Related Art
In recent years, concomitant with the trend toward higher recording density, miniaturization of recording thin film magnetic heads (inductive heads) having a core layer and a coil layer has increasingly advanced, and as a result, it has become necessary to coil a conductive material in a very small space for forming a coil layer.
Accordingly, instead of a thin film magnetic head having a spiral coil structure, it has been considered that a thin film magnetic head having a toroidal structure may become the major stream of inductive heads. The thin film magnetic head having a toroidal structure is formed by coiling a coil layer in a toroidal manner around a core layer, and the thin film magnetic head having a spiral coil structure is formed by coiling a coil layer around a connecting portion connecting a lower core layer to an upper core layer using a space formed therebetween.
In a compact inductive head formed by using a coil layer having the toroidal structure as described above, in particular, the following problems have occurred. That is, joule heat generated by recording current flowing through the coil layer described above and/or heat caused by eddy current generated in the core cannot be efficiently dissipated from the inductive head described above, and as a result, a problem has occurred in that the temperature therein is very much increased.
When the temperature inside the inductive head is increased as described above, due to the difference in thermal expansion between a coil layer and/or a core layer formed of a metal material and an insulating material surrounding the layers mentioned above, a so-called pole tip protrusion (PTP) problem may arise, that is, a portion at which the above inductive head is formed is liable to protrude from a surface facing a recording medium as compared to the other portions.
In particular, in a thin film magnetic head in which high recording density is realized, since the frequency of a recording current applied to a toroidal coil is high, the temperature inside the inductive head is rapidly increased, and as a result, the protrusion amount from the surface facing a recording medium is increased. When protruding from the surface facing a recording medium, the inductive head may be brought into contact with the recording medium more frequently, and as a result, the recording medium is liable to be damaged, and/or the inductive head is liable to be damaged.
In order to dissipate the heat generated inside the inductive head and to suppress the above PTP problem, various thin film magnetic heads have been proposed, for example, in Japanese Unexamined Patent Application Publication Nos. 2002-216314, 2001-236614, and 5-046939.
In the inductive head described in Japanese Unexamined Patent Application Publication No. 2002-216314, a heat dissipation member formed at the upper side of a lower core layer and/or a heat dissipation member formed at the lower side of the lower core layer is provided. However, since the heat dissipation member formed at the upper side of the lower core layer is covered with an insulating layer formed around a coil layer and is located at a predetermined distance from the lower core layer, heat dissipation properties of the heat dissipation member is not good enough. In addition, since the heat dissipation member is located at a position close to the coil layer, the heat generated therein cannot be easily transferred to a position far away from the coil layer, and hence an inferior heat dissipation effect can only be obtained. In addition, in the inductive head described above, the heat generated in the coil layer is transmitted to a slider through the heat dissipation member formed at the lower side (slider side) of the lower core layer and is then dissipated from this slider. However, since the number of constituent elements provided at the lower side of the lower core layer is larger than that at the upper side of the lower core layer, when a heat dissipation path is considered, the length thereof at the lower side of the lower core layer is large as compared to that at the upper side of the lower core layer, and as a result, the heat dissipation efficiency is not satisfactory. In addition, a magnetoresistive element or the like may be provided at the lower side of the lower core layer described above in many cases, and in the case described above, the heat is liable to be applied to the magnetoresistive element since being transmitted to the side at which the magnetoresistive element is provided.
In the inductive head disclosed in Japanese Unexamined Patent Application Publication No. 2001-236614, instead of a part of a lower core layer located at the height direction side, a heat dissipation member is provided at the same level as that of said part of the lower core layer; however, since this heat dissipation member is formed to have the same thickness as that of the lower core layer, there is a limit to the increase in heat capacity of the heat dissipation member. In addition, in the inductive head described above, since another heat dissipation member is formed at the lower side of the lower core layer and the above-described heat dissipation member, the heat generated in the coil layer is allowed to flow through the lower core layer or the heat dissipation member formed at the same level as that of the lower core layer and finally reaches the slider through said another heat dissipation member, and as a result, the heat is dissipated from this slider. However, since the number of constituent elements provided at the lower side (slider side) of the lower core layer is larger than that at the upper side of the lower core layer, when the heat dissipation path is considered, the length thereof at the lower side of the lower core layer is large as compared to that at the upper side of the lower core layer, and as a result, inferior heat dissipation efficiency can only be obtained. In addition, a magnetoresistive element or the like may be provided at the lower side of the lower core layer described above in many cases, and in the case described above, the heat is liable to be applied to the magnetoresistive element since being transmitted to the side at which the magnetoresistive element is provided. In addition, heat generated in the magnetoresistive element is also unlikely to be dissipated.
In the thin film magnetic head described in Japanese Unexamined Patent Application Publication No. 5-046939, a conductive member in contact with the upper surface of an upper core layer and extending to the upper side from the upper surface of this upper core layer is considered to substantially function as a heat dissipation member for dissipating heat generated in the upper core layer; however, since the area of the conductive member in contact with the upper core layer is very small, it has been believed that the heat dissipation effect is also very small.